Electric trip circuit



Sept. 18, 1951 I R. E. STURM ETAL 2,557,977

ELECTRIC TRIP CIRCUIT Original Filed Aug. '24, 1946 gYWiI/H m RALPH E. STURM JAMES R COSBY Patented Sept. 18, 1951 ELECTRIC TRIP CIRCUIT Ralph E. Sturm, Pikesville, and James R. Cosby,

Towson, Md., assignors to Bendix Aviation Corporation, Baltimore, Md., a corporation of Delaware Original application August 24,1946, Serial No. 692,892. Divided and this application October 21, 1947, Serial No. 781,228

Claims. 1

This application is a division of our application Serial No. 692,892, filed August 24, 1946, now Patent No."2',525,841, for improvements in elec- 'trical measuring circuits.

This invention relates to electrical trip circuits characterized by thepresence of a plurality of differing states of equilibrium which may be assumed under the influence of control impulses "and, more particularly, to an improved arrangement for such trip circuits in which provisions are made for eliminating response to impulses of undesired polarity, and the restoring operation is controlled through a voltage amplitude responsive conductor.

There are a number of electrical configurations known to the art characterized by the possibility of the existence of any one of a number of mutu- -ally exclusive states of electrical equilibrium assumed in response to the application of the necessary electrical stimuli. Such circuits are conveniently referred to herein as trip circuits,

for the regions intermediate the states of equilibrium are unstable, causing the circuit to pass quickly from one state to another providing discontinuous and instantaneous response. The

time between changes in the equilibrium state is frequently employed as a measure of some quantity under observation which has been translated into the form of electrical impulse spacing. For

the start of the measurement, it is necessary that the circuit always be restored to a reference condition and this is done by the application of a suitable electric impulse to the restoring terminal.

The completion of the measuring operation is signaled by the change in state resulting from the ,arrival of a trip impulse.

. Numerous such systems are known wherein the trip and restoring impulse are transmitted over separate sets of conductors or over different transmission paths on the same group of conductors. such instances entails additional expense and problems of installation which would be eliminated by a device in which the same transmission path over the same set of conductors is employed 7 .40 The multiplicity of connections required in It is a further object of the invention to provide electric trip apparatus in which the chance of a trip operation is minimized during the reset operation'and vice versa.

Still another object of the invention is to provide electric trip apparatus in which the separation of trip and restoring impulses takes place in stationary structures.

Other objects and advantages of the invention will inpart be described and in part be obvious when the following specification is read in conjunction with the drawing in which the single figure illustrates schematically the electrical circuits of a device embodying the principles of the invention.

. A plurality of thermionic valves is illustrated, each provided with an electron emissive cathode brought to operating temperature by an associated heater. Neither the heaters nor the circuits for energizing same have been illustrated in the interest of preserving simplicity of presentation, since any of the many conventional heater configurations may be successfully employed.

In the circuit illustrated, operating potentials are derived from the battery I2 having its negative terminal connected to ground and its positive terminal connected to one end of a voltage divider M, the other end of which is also grounded. The voltage divider I4 is tapped at several intermediate points to provide a number of operating voltages whose purpose will be evident from their names and from the following descriptive material. The lower tap l6 serves to provide operating bias for three discharge valves and may hence be termed the bias tap l6. Next in the order of increasing positive potential there is the measuring circuit tap I 8 supplying energy to the measuring bridge. In practice the voltage of measuring tap It with respect to ground has been set at approximately volts.

The next higher voltage tape is the reset blocking tap 20 which may have a potential of approximately v. with respect to ground. This voltage prevents operation of the reset circuit during the measuring cycle. Line 22 is at the battery terminal potential, which may be volts.

Voltage from the measuring circuit tap 18 passes through lead 24 and lead 26 in the measuring station cable 28 to a measuring station 21 which may contain fixed resistors 30 and 32 in capacitor 96.

series with a potentiometer 34 having a movable tap 36 adapted for actuation by hair element 38. As the hair element changes in length, tap 36 moves to and fro over potentiometer 34 varying the potential applied to lead 40 running through and from the measuring station cable 28. The ground circuit return for the measuring station is provided by lead 42 running through cable 28 to the chassis of the voltage comparing portion of the apparatus.

It will be apparent that the element so far described is one for translating changes in humidity into changes in electric voltage. Variables other than humidity may be similarly measured by use of appropriate condition responsive elements driving variable resistors or by theuse of resistors or other circuit elements themselves directly responsive to the condition being monitored. v

The lead 46 from the measuring stationis connected with the anode 44 of the diode 46 through a bridge signal resistor 48, shunted at its cable end by a capacitor 50 to minimize the response of the apparatus to stray electric transients ap- -:pearing inthecable 28. There isassociated with anode :44 a thermionic cathode 52 connected through secondary 54 of transformer 56 to the movable arm 69 of a search-voltage potentiom- "eter 58. The .primary62 of transformer 56 may be energized from any suitable alternating current source '64 to impress on cathode 52 a corresponding alternating voltage.

One terminal of the winding of search voltage potentiometer 58 is grounded at 66 while the other terminal 68 is connected to the measuring voltage line'24. The resistive element of potentiometer 58 occupies less than the entire 360 arc and anauxiliary contact 10 connected with the battery line 22 is situated within the unused portion of the arc. A motor 12 drives .the potentiometer arm 60 continuously in a clockwise direction, as indicated, whereby the arm 60 successively engages the entire length of the winding of potentiometer 58 and momentarily engages the aux- 'iliary contact 18 during its passage thereby. A

character bearing disk 14 is rotated synchronously with potentiometer arm 60 by motor 12 and a printed strip 16 associated with the character bearing wheel 14 is periodically driven into (maximum positive measuring circuit potential by the connection of a stabilizing resistor 1|, of the order of a megohm or more, between arm 60 and the measuring voltage line 24.

The signals from the balance responsive circuit pass through lead 84 and coupling capacitor 86 to the control grid 88 of amplifier valve 90 through a resistor 92. The junction of capacitor 86. and resistor 92 is connected to ground through the grid leak resistor 94, and the control grid end of resistor 92 is shunted to ground by a filter The amplifier valve 90 has a cathode 9| connected to a suppressor grid 93 and grounded through cathode resistor 95 to provide operating bias on control grid 88. A space charge grid 98 is situated intermediate control grid 88 and suppressor grid 93, and energized from the battery line 22 through droppin resistor I and lead I02. The power supply to space charge grid 98 is filtered for alternating components by the connection of capacitor I04 between the grid 98 and ground.

An anode I06 is located exteriorly of the element assembly so far described in connection with vacuum tube 90 and connected with the battery line I82 through a load resistor I08. Anode circuit filtering discriminating against transient signalcomponents is afforded by the connection of capacitor III! between the anode I06 and ground. Signals appearing in the anode circuit of valve 90 are transferred to subsequent stages through the coupling capacitor II2 connected between anode I06 and a grid leak II4 having its remote end grounded. A limiting resistor H6 connects the junction of capacitor H2 and grid leak II4 to the control grid II8 of a gaseous discharge trip valve I20. The control grid I I8 is shunted to ground by filter capacitor I22. and by a diode I24 so poled that the control grid H8 is restrained from becoming negative with respect to ground. Improved stability is afiorded by the connection of a capacitor I26 between control grid H8 and the thermionic cathode I28 of discharge valve I20. A shielding grid I38, situated within discharge tube I20 intermediately of control electrode H8 and anode I32, is directly connected electrically with cathode I28. The anode I32 of the trip valve I20 is connected with the battery line I82 by a resistor I34 and the high voltage anode circuit is completed by the connection of a cathode resistor I36 between cathode I28 and bias tap I6 via line I31. Cathode resistor I36 is shunted by capacitor I38 to improve the commutating properties of the two tube back to back coupled flip-flop circuit as more fully described in the copending application of James R. Cosby, filed August 8, 1946, Serial No. 689,109, now Patent No. 2,549,667.

The flip-flop circuit resetting is performed by reset valve I62 having a cathode I64 connected through lead I31 to the bias tap I6 and havin a shield grid I66 connected directly to cathode I64. On the side of shield grid I66 remote from cathode I64 there is situated an anode I68 which is connected to battery line I02 through anode resistor I10. Anode I68 of reset valve coupled to anode I32 of trip valve I20 by commutating capacitor I15 connected therebetween.

A control grid electrode I1I situated between cathode I64 and shield grid I66 serves to control the discharge within the reset valve I62 in response to signals arriving through capacitor I16 connected between control grid I18 and the oathode I12 of the reset diode I14. A direct current return path for control grid I1I is provided by leak resistor I18 connected between control grid HI and ground.

Again undesired response to stray electric transients is prevented or minimized by a capacitor I shunted between control grid HI and cathode I64.

It may be noted in passing that no appreciable impedance is inserted in the return circuit from cathode I64 and bias tap I6, thus permitting the omission of the precautionary circuit features described in the aforementioned copending application at this point in the circuit. However, the resistor I36 in the cathode return of trip valve I28 gives rise to a positive trigger pulse at the moment of breakdown of trip valve I20. A capacitor I40 connected between cathode I28 of trip valve I20 and the ungrounded end of grid I62 is v leak resistor I48 impresses the trigger pulse occurring in this portion ofthe circuit on the con- .trol grid I42 of relay control valve I44 through the limiting resistor I46. The relay control valve I 44 may, like the tubes in the previously described flip-flop circuit, be of the gaseous-filled type commercially designated Thyratron. A shield grid I54 within the relay control valve I44 is directly connected with the thermionic cathode I52, and exterior to this electrode assembly there is situated an anode I60, connected with the positive terminal of the anode source I2 by the limiting resistor IN. The winding of a relay I56 connects cathode I52 with bias tap I6 and a reservoir or storage capacitor I58 is shunted between anode I60 and the tap end of the winding of relay I56. A capacitor of 4 mid. has

been found adequate for the storage capacitor I56. The relay I56 carries a pair of normally open contacts connected in series with the solenoid relay 82 and a tapper bar energizing source I 63. In practice the tapper bar energizing source I63 and the balance signal source 64 may be the same, but there may exist conditions making it desirable to use commercial line frequencies in the circuit of tapper bar energizing source I62 and some other different frequency for the balance signal source 64 to prevent interference of the power circuits with the balance signal circults.

The reset diode I14, previously referred to, is arranged in a circuit such that a reset impulse is applied to control grid I1I only during the passage of the arm 60 across the reset tap 10 on potentiometer 58. The cathode I12 of diode I14 is re-,

turned to the reset blocking tap through a resistor I82 and the anode I13 of diode I14 is connected with the rotating arm 60 of potentiometer 58. As the positive potential applied to cathode I12 from reset blocking tap 20 is higher than the maximum positive potential existing at any point on the winding of potentiometer 58, there can be no passage of electric current through the reset diode I14 during the measuring portion of the operating cycle. For a portion of its rotation, the arm 60 fioats" which is to say that it is disengaged electrically from all portions of potentiometer 58. During this period, the anode I13 has its potential fixed by the leak resistor II connected between arm 60 and measuring circuit tap I8. The arm 60 and its associated circuits is thereby held at a potential low enough to prevent conduction through the reset diode I14 and, at the same time, high enough to also prevent conduction through the balance sensing diode 46.

With the foregoing mutually cooperative relationship of the parts in mind, the operation of the apparatus may now be readily understood.

The motor 12 drives the potentiometer arm '60.

and printer wheel 14 continuously. The lead 40 impresses on anode 44 a direct current potential indicative of conditions existing at the measuring station 21. This potential will always lie between 0 and volts. As the arm of potentiometer 58 is rotated, it impresses on cathode 52 of the balance signal diode 46 a search potential varying periodically from 0 to 50 volts in smooth continuous fashion, the search voltage starting at 50 volts positive with respect to ground and decreasing gradually to 0. At some point during this variation, the voltage at cathode 52 becomes very nearly equal to that existing at anode 54, whereupon the alternating potentials superimposed on cathode 52 periodically drive cathode 52,

negative with respect to anode 54 producing a pulsating current in the lead attached to anode 44. These pulses develop a corresponding pulsating voltage across the bridge signal resistor 48 which passes through the signal amplifier valve where its voltage excursions are amplified and then impressed on the trip valve I20. A discharge is now initiated in the valve I20 producing a positive pulse in its cathode circiut which then initiates a discharge in relay control valve I44. Breakdown of the relay control valve I44 discharges reservoir capacitor I58 through relay I 56, momentarily closing the contacts of relay I56 and instantaneously energizing the solenoid 82 from source I62 to drive the tapper bar 18 against the printing strip I6, carrying it into engagement with the printer wheel 14 to print on the strip 16 a figure indicative of the angular position of arm 60 of the potentiometer 58 at the time when the search voltage developed from potentiometer 58 was equal to the measuring station output. As a given measuring station output voltage corresponds to a predetermined value of the condition under measurement, the printer wheel may be directly calibrated to indicate the condition value at this time.

' Continuing rotation of potentiometer arm 60 decreases the direct current voltage component at 52 still further, thus increasing the signal input to control grid I I8 of trip valve I20. The control grid H8 is alternately driven positive and negative. The anode current passing through the trip valve I20 is limited by resistors I34 and I36 and, hence, there is danger that the application of negative signals to control grid II8 may interrupt thedischarge flowing through the trip valve I20, which might give rise to successive erroneous printing operations. The possibility of such an occurrence is eliminated by the connection of clamping diode I24 between control grid H8 and ground with the diode anode connected to ground. Upon the arrival of a signal of negative polarity at grid II8, conduction in the diode I24 is established to limit the negative signal excursion and prevent the interruption of the arc discharge within trip valve I20.

Continuing rotation of the potentiometer arm 60 disengages the arm 60 from the active'elements of the potentiometer. At this time, current flowing through stabilizing resistor II brings the potential of arm 60 and its associated circuits to the maximum measuring circuit potential, approximately 50 volts, with respect to ground. This potential insures that alternating current signal transmission through the balance signal diode 46 is prevented and, at the same time, maintains anode I13 of the reset diode I14 negative with respect to its cathode I12, preventing operation of the reset circuit. With the further movement of the potentiometer arm 60, the reset contact 10 is traversed, momentarily raising the arm circuit potential to the full anode supply voltage of volts, swinging anode I13 positive with respect to cathode I12 to develop across reset diode load resistor I82 a 50-volt pulse triggering the reset valve I62 through coupling capacitor I16 to establish a discharge in the reset valve I62 and extinguish that in trip valve I20. This arm voltage of 150 volts carries the cathode 52 of balance signal diode 46 still further positive with respect to its associated anode, preventing operation of the signal circuit at this time. This prepares the circuit for a repetition of the measuring operation which is initiated with the re-engagement of the winding of potentiometer answer? 7 58 by the potentiometer arm 60 in its subsequent rotation.

Values of circuit components which have been found suitable for making observations at the rate of 2 per minute follow:

:Balance signal resistor 48, 220,000 ohms Line filtercapacitor 50, 1 mid. Stabilizing resistor II, megohms Coupling capacitor 86, .05 mfd. Limiting resistor 92, 100,000 ohms .Grid leak resistor 94, 220,000 ohms Grid filter capacitor 96, .01 mfd.

Grid dropping resistor I00, 1.5 megohms Anode load resistor I08, 220,000 ohms mmfd.

Storage capacitor I58, 4 mfd.

Limiting resistor IBI, 470,000 ohms Reset anode resistor I10, 220,000 ohms Gommutating capacitor I15, .01 mfd.

Reset input coupling capacitor I16, .05 mfd. Reset input filter capacitor I80, 250 mmfd. .Reset diode load I82, 220,000 ohms While the trip apparatus illustrated as controlling the operation of the tapper bar incorporates a pair of vacuum tubes, it is to be under- .stood that the use of any type of trip apparatus characterized by at least two conditions of equilibrium separated by a region of instability is contemplated, in which one or the other of the .two stable conditions may be established by the application of trip and reset pulses to the proper input terminals. It is further obvious that the device or devices responsive to the output of this measuring circuit may respond as visual indicators 'or may indicate their response by effecting a control operation. The term indicating device as used herein is intended to embrace both types of operation.

The foregoing has made the essence of the invention clear and there willbe apparent to those .skilled in the art many modifications and applications which do not distinguish substantially therefrom. I

What is claimed and desired to be secured by United States Letters Patent is:

'1. In combination with electric trip apparatus sensitive to the polarity of electric pulses applied ';thereto having trip and restoring terminals and an input .terminal, a source of voltage varying in magnitude through a predetermined range connected to said input terminal; means including a first unilaterally conductive impedance connon conductive in a second range of voltage of said source higher than said first range; means including ,a second unilaterally conductive impedance connected between said input terminal landsaid restoring terminal for transmitting an '"elec'tric pulse to said restoring terminaL-sa id sec- 0nd impedance'being conductive in said second range of voltage of said source; and 'means for impressing a steady bias voltage on said second impedance, said bias voltage being higher than said first-range of'voltage of said source.

' 2. In combination with electric trip apparatus sensitive to the polarity of electric pulses applied thereto having trip and restoring terminals and an input terminal, a source of voltage varying in magnitude through a predetermined range connected to said input terminal; means including a unilaterally conductive impedance connected .between said input terminal and said trip terminal vfor transmitting an electric :pulse to said trip terminal, said impedance being conductive in a first range of voltage of said source and non-conductive in a second range of voltage of said source higher than said first range, means including a second-unilaterally conductive impedance connected between said input terminal and said restoring terminal for transmitting an electric pulse to said restoring terminal, said second impedance being conductive in said second range of voltage of said source; means for impressing. a steady bias voltage on said second unilaterally conductive impedance, said bias voltage being higher than .said first range of voltage; and a third unilaterally conductive impedance connected between said first impedance and said trip terminal.

3. In .combinationwith electric trip apparatus having trip and'restoringterminals and .an input terminal, a source of voltage varying in :magnitude through a predetermined :range connected to said input terminal; first and second unilaterally conductive devices connectedinseries in the same sense between said trip and restoring terminals, means connecting the common terminals or" said unilaterally conductive devices with said input terminal, said first device being conductive in a first range of voltage of said source for transmitting an electric pulse to said tripterminal and said second device being conductive in :a second range of voltage of said source higher than said first range for transmitting an electric pulse to said restoring terminal, said first device being non-conductive in said second range of voltage 'of said source; and means for impressing .a steady bias voltage across said second device, said bias voltage being higher than said first range :of voltage.

4. 'In combination with electric trip apparatus having trip and restorin terminals and an input terminal, a source of voltage varying in magnitude through'a predetermined range connected to said input terminal; first and second unilaterally conductive devices connected in series in non-conductive in said second range of voltage of said source; means for impressing a steady bias voltage across said second device, said bias voltage being higher than said first range of voltage, and a third unilaterally conductive device connected between said first device and said trip terminal.

"5. --In*'combination with electric trip apparatus having trip and restoring terminals and an input terminal, a source of voltage varying in magnitude through a predetermined range connected to said input terminal, means including a first diode connected between said input terminal and said trip terminal for transmitting an. electric pulse to said trip terminal, said first diode having its cathode connected to said input terminal; means including a second diode connected between said input terminal and said restoring terminal for transmitting an electric pulse to said restoring terminal, said second diode having its anode connected to said input terminal; said first diode being conductive in a first range of voltage of said sourceand being non-conductive in a second range .of voltage of said source higher than said first range and said second diode being conductive in said second range of voltage of said source; and means for impressing a steady bias voltage across said second diode, said bias voltage being higher than said first range of voltage.

RALPH E. STURM. JAMES R. COSBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,778,465 Ozanne Oct. 14, 1930 1,979,484 Mathes Nov. 6, 1934 2,210,523 I Blumlein M Aug. 6, 1940 2,211,751 Humby et al Aug. 20, 1940 2,266,401 Reeves Dec. 16, 1941 2,348,016 Michel May 2, 1944 2,365,450 Bliss Dec. 19, 1944 2,366,038 Livingston Dec. 26, 1944 2,370,178 Livingston Feb. 27, 1945 2,405,930 Goldberg et al Aug. 13, 1946 2,421,018 De Rosa May 27, 1947 2,425,063 Kahn et al Aug. 5, 1947 2,432,188 Bliss Dec. 9, 1947 2,442,403 Flory et al June 1, 1948 2,469,860 Cockrell May 10, 1949 

